Pneumatic leak detector with improved nozzle

ABSTRACT

A pneumatic leak detector operates by submerging a nozzle in oil. Airflow from the nozzle results in simultaneous cavitation and atomization of the oil. Microscopic oil droplets form a fog, which is used to detect leaks in closed duct systems. The integrated valve and nozzle includes a stem on one end for air input, the nozzle on the other end for air output, and a check valve between the stem and the nozzle to prevent the backflow of air or oil. The exterior body of the integrated valve and nozzle is a convex body wedge. A smaller concave wedge is cut at the orifice of the nozzle. The critical parameters of the nozzle are its orifice diameter, body wedge angle, orifice cut angle, and orifice cut depth, all of which have been optimized by experimentation to yield maximal fog density.

1. FIELD OF THE INVENTION

This invention is in the field of airflow valves and nozzles,specifically for atomizing fluid into fog.

2. BACKGROUND OF THE INVENTION

A leak detector is a device for detecting leaks in closed duct systemssuch as HVAC ducts or automotive engines, intakes, exhaust pipes, gastanks, or evaporative emission control systems. A leak detector producessmoke or fog. The smoke or fog is channeled into a closed system. If thesystem has any leaks, the smoke or fog will emerge from the leak pointsfor easy visual identification.

This invention is a leak detector that produces fog for detecting leaks,ideally in automotive systems.

3. DESCRIPTION OF RELATED TECHNOLOGY

Traditional automotive smoke machines heat mineral oil to the smokepoint temperature. At this temperature, the liquid mineral oil isatomized into particulate smoke. This method requires a high amount ofenergy, most of which is lost as heat. In addition, the output smoke ishighly carcinogenic due to the oxidation of mineral oil caused byoverheating. The smoke is extremely uncomfortable to breathe. Directlybreathing the output smoke can cause eye, nose, and lung irritation.

U.S. Pat. 6,907,771 (Finlay and Clumpus) describes a leak detector thatproduces fog by directing pressurized air at the surface of a fluid. Thepressurized air emerges from a nozzle suspended a small distance abovethe fluid. This pneumatic technology eliminates the problems associatedwith energy consumption, waste heat, and carcinogenic smoke.

4. SUMMARY OF THE INVENTION

The present invention is a pneumatic leak detector with an improvednozzle. The nozzle is designed to operate while submerged in fluid(ideally oil), rather than being suspended above the fluid. It producesfog by forcing air through a special orifice. The nozzle geometrymaximizes fog density by minimizing particle size. A check valveprevents backflow of air or fluid into the air source.

As pressurized air exits the nozzle and contacts the fluid, it formsbubbles that float up to the surface of the fluid. Simultaneously, thenozzle atomizes the oil into tiny particles, like a garden sprinkler.The atomized oil (“fog”) is trapped inside the bubbles. Thus, when thebubbles reach the surface of the oil and burst, they release fog intothe fluid chamber. The fog accumulates pressure so that it isautomatically forced out of the output of the fluid chamber.

5. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the components of the pneumatic leak detector in aperspective view.

FIG. 2 is a cross-sectional view of the nozzle assembly operating withina fluid chamber.

FIG. 3 is an external view of the nozzle assembly in isolation.

FIG. 4 is a detailed cutaway view of the nozzle assembly.

FIG. 5 is a detailed cross-sectional view of the distal end of thenozzle.

6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 presents the major components of a pneumatic leak detector 10.The system is mounted on a base mounting plate 101. A DC electric airpump 102 takes in atmospheric air through the air pump input 1021,pressurizes the air, and expels the pressurized air through the air pumpoutput 1022. The air pump is driven by a power source such as a batteryor a generator. The pressurized air is directed through conduit 103,which passes into fluid chamber 104. The fluid chamber is partiallyfilled with fluid 106, which is ideally an oil. The conduit is connectedto the nozzle assembly 105, which is partially or entirely submerged inthe fluid 106. The entire leak detector 10 is ideally contained within ahousing.

The air pump can be used for additional purposes such as pressure andflow testing. Therefore, a solenoid valve can be added between the airpump output and the nozzle assembly, to vary the direction of air flow.Regardless of configuration, the air from the air pump output musteventually enter into the nozzle assembly. The conduit 103 can passthrough check valves, splits, fittings, or other airflow regulatorsbetween the air pump output 1022 and the nozzle assembly 105.

FIG. 2 depicts the pneumatic operations within the fluid chamber 104.The nozzle assembly 105 is positioned at the fluid chamber input 1041.Stem 1053 protrudes outside the fluid chamber, while the nozzle 1052 issituated within the fluid chamber. The level of the fluid 106 should beat least as high as the nozzle 1052, so that air exiting the inventioncomes into immediate contact with the fluid. A check valve 1051 may beintegrated into the nozzle assembly. Alternatively, the check valve maybe separate from the nozzle assembly, in which case the valve and thenozzle assembly would be connected by air tubing. Pressurized air in theair tubing conduit would progress from the air pump output to the checkvalve, and then from the check valve to the nozzle assembly.

Pressurized air 21 enters the nozzle assembly from the conduit 103(omitted from FIG. 2 ) into stem 1053. The air passes through the checkvalve 1051 and exits the nozzle 1052. As the air contacts the fluid 106,cavitation and atomization occur simultaneously. Air bubbles 22 form atthe mouth of the nozzle and rise to the surface of the fluid. Meanwhile,the fluid around the mouth of the nozzle is dispersed into atomizedfluid particles 23 (small, but not necessarily literally atoms). Thefluid particles occupy the air bubbles; as the bubbles breach thesurface of the fluid and burst, the atomized fluid particles arereleased into the airspace 24 inside the fluid chamber. The atomizedfluid particles form a fog within the airspace 24. As they accumulate,the vapor pressure of the fog increases. The vapor pressure soon exceedsatmospheric pressure, at which point fog emerges from the fluid chamberoutput 25. This fog is directed through an exit conduit (not shown) andthen into a closed duct system as described above.

The exterior of the nozzle assembly 105 is best seen in FIG. 3 , whilean embodiment of its internal features is presented in FIGS. 4 and 5 .The nozzle has a cylindrical bore 10521, which opens into a concavenozzle wedge 10522. The exterior of the nozzle assembly, near the nozzlewedge, is shaped as a convex body wedge 1054.

The features of the nozzle are shaped and sized to critical dimensions.The diameter of the cylindrical bore is the orifice diameter 105211,seen best in FIG. 5 . The angle between the faces of the body wedge 1054is the body wedge angle 10541, seen best in FIG. 4 . The angle betweenthe faces of the nozzle wedge 10522 is the orifice cut angle 105221,best seen in FIG. 5 . The depth of the nozzle wedge is the orifice cutdepth 105222, best seen in FIG. 5 .

Experimentation has shown that the orifice diameter 105211 is ideally0.51 mm, with an acceptable range of 0.30 mm to 1.20 mm. This rangecreates ideal airflow; airflow is too low for diameters below 0.3 mm andtoo high for diameters above 1.2 mm. A smaller diameter causes weakoutput; it is also hard to manufacture. A larger diameter results in lowfog density with a small mist-to-air ratio.

The nozzle wedge 10522 is a highly critical feature; mist density can beup to 80% lower without it. Experimentation has shown that the orificecut angle 105221 is ideally 90°, with an acceptable range of 30° to130°. Smaller angles create challenges in manufacturing the orifice.Larger angles result in decreasingly dense fog.

The orifice cut depth 105222 is ideally 1.2 mm, with an acceptable rangeof 0.4 mm to 3.0 mm. A cut depth outside of this range reduces mistdensity by up to 40%.

The body wedge 1054 helps expose and increase the surface area of thenozzle wedge 10522. Current embodiments of the invention have proven towork best with a body wedge angle 10541 of approximately 90°, with anacceptable range of 50° to 140°.

FIG. 4 shows an embodiment of the check valve 1051. The check valveensures that air, fog, and fluid cannot pass backward or upstream fromthe nozzle 1052 toward the pump 102. Nozzles and valves are bothcommonly manufactured items, but the known prior art has not revealed avalve integrated into a nozzle.

The check valve includes a soft rubber disc 10511 positioned in linewith the internal airflow 41. Forward airflow bends the soft rubber discin a downstream direction, thus allowing air to continue flowingdownstream. The disc has room to bend in this direction due to the valvespace 10513. Valve floor 10512 prevents the soft rubber disc frombending in the upstream direction. This effectively blocks fluids fromflowing in reverse past the check valve.

Experimentation has shown that the quantity and quality of the vapor areoptimized when the air exits the nozzle at a pressure of 3 - 9 PSI and aflow rate of 1 - 7 liters per minute.

I claim:
 1. A system for detecting leaks in a conduit, comprising: a DCelectric air pump; a check valve connected to the DC electric air pumpby air tubing; a fluid chamber; a nozzle assembly within the fluidchamber and connected by air tubing to the check valve; said nozzleassembly comprising an interior, an exterior, a proximal end, a stem atthe proximal end, a distal end that assumes the form of a convex bodywedge, and a nozzle at the distal end; a housing to house the DCelectric air pump, check valve, fluid chamber, and nozzle assembly; anexhaust port in the housing, such that the fluid chamber opens into theexhaust port.
 2. The invention of claim 1, further comprising a concavenozzle wedge cut into the nozzle.
 3. The invention of claim 2, whereinthe nozzle comprises an orifice with an orifice diameter; and theorifice diameter is between 0.3 mm and 1.2 mm, inclusive.
 4. Theinvention of claim 3, wherein the nozzle wedge opens at an angle between30° and 130°, inclusive.
 5. The invention of claim 4, wherein the nozzlewedge is cut at a depth between 0.4 mm and 3.0 mm, inclusive.
 6. Theinvention of claim 5, wherein the body wedge is cut at an angle between50° and 140°, inclusive.
 7. The invention of claim 6, wherein the checkvalve is integrated into the interior of the nozzle assembly.
 8. Theinvention of claim 7, the check valve comprising a conduit connectingthe stem to the orifice in the interior of the body; a flexible rubberdisc concentric with the conduit; a valve space distal to the flexiblerubber disc, to allow air to flow in the proximal-to-distal directionaround the flexible rubber disc; and a valve floor proximal to theflexible rubber disc, to prohibit the flow of fluid in thedistal-to-proximal direction around the flexible rubber disc.
 9. Theinvention of claim 8, further comprising at least one airflow regulatorin the conduit between the air pump output and the nozzle assembly. 10.The invention of claim 9, in which the at least one airflow regulator isselected from the group consisting of a solenoid valve, a split, and afitting.
 11. A method of producing vapor, comprising the steps ofproviding a chamber of oil with a surface; submerging a nozzle below thesurface of the oil; pumping air through the nozzle to atomize the oilinto vaporous particles; and collecting the vaporous particles in thechamber above the surface of the oil.
 12. The method of claim 11, inwhich the air is pumped through the nozzle at a pressure of 3 to 9 PSI,inclusive.
 13. The method of claim 12, in which the air is pumpedthrough the nozzle at a flow rate of 1 to 7 liters per minute,inclusive.